Field of the Invention
The present invention relates to an anisotropic conductive film capable of electrically and mechanically connecting an electronic component, such as an IC chip, a liquid crystal display panel (LCD panel) of a liquid crystal display (LCD), and relates to a method for producing the anisotropic conductive film, a connection method and bonded structure using the anisotropic conductive film.
Description of the Related Art
Conventionally, a connecting material in the shape of a tape, obtained by coating a release film with a thermoset resin containing conductive particles dispersed therein (e.g., anisotropic conductive film (ACF; Anisotropic Conductive Film) has been used as means for connecting an electronic component with a substrate.
This anisotropic conductive film is used, for example, in a case where various terminals are bonded as well as electrically connected to each other, including when a terminal of a flexible print substrate (FPC) or IC chip is connected with an indium tin oxide (ITO) electrode formed on a glass substrate of a LCD panel.
Recently, an electronic component has been much downsized, and more integrated. Therefore, a pitch between adjacent electrode in the electronic component has been smaller (more fine-pitched). Most of electroconductive components used in an anisotropic conductive film are spherical, and those having diameters of several micrometers or larger are commonly used. When an electrode of an electronic component, which is downsized, integrated, and has a small pitch between electrode, is connected using the aforementioned anisotropic conductive film, there is a problem that insulation resistance between the adjacent electrodes (terminals) is not sufficient. Therefore, there is a need for achieving excellent conduction resistance, and insulating resistance between adjacent terminals in anisotropic conductive connection in a fine pitch.
As for a technique associated with a fine pitch, disclosed is an anisotropic conductive material, which can be used for connection between substrates and for a pressure sensitive sensor, and in which a metal powder composed of metal particles linked in the form of a chain is dispersed in a rubber material (see Japanese Patent Application Laid-Open (JP-A) No. 2003-346556).
In accordance with this technique, however, there is a problem that a short circuit is caused as particles of the metal powder are in contact with each other at the time of anisotropic conductive connection, and insulation resistance between adjacent electrode in a substrate or electronic component cannot be sufficiently maintained. Since a number of metal particles to be linked is not specified, moreover, there are particles in a chain, which do not effectively function for anisotropic conductive connection, and therefore a particle capturing rate tends to be low.
Moreover, disclosed is a connection method using an anisotropic conductive member, which contains: placing an isotropic conductive member containing conductive particles including a magnetic component, between two substrates on which a conductor pattern to be connected has been formed; applying a magnetic field to control an oriented state of the conductive particles; and heat bonding the two substrates (see JP-A No. 2004-185857).
In accordance with this technique, however, a magnetic field is applied during anisotropic conductive connection. Therefore, a large number of the conductive particles are linked in the form of a chain due to the applied magnetic field, As a result, insulation resistance between adjacent electrodes in a substrate or electronic component cannot be sufficiently maintained, and therefore there is a problem that a short circuit is caused. As a large number of the conductive particles are linked in the form of a chain, moreover, there are conductive particles in a chain, which do not effectively function for anisotropic conductive connection, and therefore a particle capturing rate tends to be low.
Accordingly, there are currently needs for an anisotropic conductive film, which can attain insulation resistance between adjacent terminals in anisotropic conductive connection of fine-pitch, and can achieve anisotropic conductive connection, which excels in conduction resistance and a particle capturing rate, as well as a method for producing the anisotropic conductive film, and a connecting method and bonded structure using the anisotropic conductive film.